添加javascript src和文本javascript有什么区别？

添加的区别是什么

<script type="text/javascript" src="helloworld.js"> 

}))

<script type="text/javascript">document.write("Hello World"); //content of helloworld.js</script>    

Ext.apply(Ext.Loader, {
  injectScriptElement: function(url, onLoad, onError, scope, charset) {
        var script = document.createElement('script'),
            me = this,
            onLoadFn = function() {
                me.cleanupScriptElement(script);
                onLoad.call(scope);
            },
            onErrorFn = function() {
                me.cleanupScriptElement(script);
                onError.call(scope);
            };

        script.type = 'text/javascript';
        //script.src = url;
        script.text = me.getContentFromDatabaseByUrl(url);
        script.onload = onLoadFn;
        script.onerror = onErrorFn;
        script.onreadystatechange = function() {
            if (this.readyState === 'loaded' || this.readyState === 'complete') {
                onLoadFn();
            }
        };

        if (charset) {
            script.charset = charset;
        }

        me.documentHead.appendChild(script);

        return script;
    }